Process for dyeing and aftertreating polyethylene oxide modified nylon fibers



United States Patent PROCESS FGR DYEING AND AFTER'IREATING POLYETHYLENE ()XIDE MODIFIED NYLON FIBERS Isaac Fletcher Walker, Hockessin, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware N0 Drawing. Filed Oct. 31, 1962, Ser. No. 234,551

6 Claims. (Cl. 855) polyamide fibers thus modified have relatively poor dye lightfastness. Even when using acid and premetallized acid dyes which are most durable on unmodified nylon, unsatisfactory lightfastness results are obtained. In addition, it has been found that these dyes are thermally instable when applied to the antistatic poly'amide fiber. This deficiency is serious in carpets which must be heated when the latex binder is cured and in fabrics which must be heat set. Even long term use in heated locations may lead to thermal dye fading.

It is an object of this invention to provide antistatic, PEG-modified, polyamide fibers having improved dye lightfastness. It is another object of this invention to provide for improved thermal dye stability in dyed anti static polyamide fibers.

These objectives are attained in a nylon fiber which contains at least 2% by weight of a polyethylene oxide of at least 600 molecular weight, which fiber is dyed with an acid dyestutf and impregnated with at least 100 p.p.m. (based on weight of polyamide) of copper as a cupric salt.

In one process embodiment, the required amount of cupric ion is added to the dye bath. In a second, preferred embodiment, the cupric ion impregnation is accomplished in a hot water bath after dyeing. In both embodiments, the impregnation bath contains at least about 1% OWY of a substantially neutral ionizable surface active wetting agent.

For dyeing procedures which do not require a pH above about 8.5, it is only necessary to add from l5%, based on weight of nylon yarn (OWY), of a water-soluble cupric salt to the dye bath. Otherwise, the salt is not added until the pH has been reduced to less than 8.5 (Example I). When the dye bath pH is relatively high, e.g., in the range of 89, to maximize dye exhaust and minimize staining from such components as the jute backing of carpets, it is often desirable to complex the cupric ion with oxalic acid, tartaric acid, ammonium ion complexes and the like. Either such treatment will introduce (via diffusion) from 100 to 3,000 parts per million (ppm) of the cupric ion into the fiber. Of course, the dye bath will also contain the customary additives (including dye) such as leveling salts, buffers, acids, bases, wetting agents and the like.

The preferred method (Example VI) of impregnating the PEG-modified polyamide fibers with the cupric ion is to add from l5% OWY of a water-soluble cupric salt to a post-dye water bath. This procedure is especially desirable for jute-backed carpets, since mild rinse conditions can be employed, thereby minimizing jute-staining. It is essential that at least about 0.5% OWY of a surface active wetting agent such as the sodium salt of an unsaturated long-chain alcohol sulfate also be present in the water bath.

It should be noted that the process disclosed herein differs from the well-known cuprous ion dyeing of polyacrylonitrile fibers in that use of the cupric ion in the polyacrylonitrile process has the deleterious effect of causing areas of reduced dyeability and poor dye uniformity. Moreover, cupric ions formed in that process, as by oxidation, may be converted to black cupric oxide when heated, thus discoloring the dyed fabric. In contrast, the presence of cuprous ions in the present process improves the dye lightfastness of some shades but actually decreases the dye lightfastness of others. The beneficial effect of the cupric ion in improving dye lightfastness of PEG-modified nylon appears to be unique among metal ions since it consistently improves the dye lightfastness of a wide variety of dyes.

The mechanism by which the cupric ion protects the dye is not known. It is surprising that the manganous ion, which is effective to a lesser degree, is in its lowest valence state, While the copper must be in its highest valence. Many metal ions have no efiect, while others act as dye sensitizers, accelerating fading.

Those dyes which are known as neutral dyeing or premetallized acid dyes are especially suitable for use with PEG-modified nylon fibers which are to be treated in accordance with the present invention. Typical examples include the mono-azo dyes which are half metallized, i..e., two dye molecules are complexed to divalent metal such as chromium or cobalt. The dye is complexible by virtue of hydroxy or carboxy groups in the O or 0' positions with respect to the azo group and is water-soluble by virtue of sulfamoyl groups and/or the metal ions of the complex. Examples of such dyes are described in US. Patents 2,671,081, 2,885,392, and 3,051,- 696. In some cases, acid dyestuffs not previously reacted with -a metal ion are employed. To be suitable, there can be no change in shade in the event of any reaction between the dyestuff and cupric ion during impregnation. Such acid dyes are used in the exemplified dye mixtures.

The process of the instant invention is useful in improving dye lightfastness when a single dyestutr' is used, to produce a self shade. The process is also useful when a number of dyestuifs are mixed to provide a compound shade of the desired color. In the latter usage, dye lightfastness requirements are high since it is essential to retard fading of each of the dyes in the mixture in order to avoid a color change on exposure to light. Some improvement in dye lightfastness has also been noted when the cupric salt is used after a dispersed dye treatment.

The substrates particularly operable in the process of this invention are synthetic linear polymers characterized by recurring amide linkages as integral parts of the polymer chain. These polyamides are produced by condensation of monoamino, monocarboxylic acid and their amide-forming derivatives, or of diamine and dicarboxylic acids or their amide-forming derivatives. Examples of the first group are polycaprolactam and polyaminoundecanoamide. Examples of the second group are poly=(hexamethylene adipamide), poly(hexamethylmethylene adipamide and extruded to a 68 filament yarn which is subsequently drawn to produce a 1040 denier final product. This yarn is steam bulked, as described by Hallden in U.S. 3,005,251, and tufted into a plain,

ene sebacamide), poly(m-xylene adipamide), po1y(p-xy- 5 looped pile, jute-backed carpet, switches of which are 'lylene sebacamide), poly(Z-methylhexamethylene adipused in the dyeing and light exposure tests described hereamide) and the polyamide from bis(p-aminocyclohexyl) inafter.

methane and sebacic acid. Copolyamides within or For the various runs reported in Table I, the dye among these groups may also be employed. With these bath to carpet yarn weight ratio is 50-100 to one. The polyamides are melt blended at least 2% by weight of baths contain 1% ammonium hydroxide, 12% ethylene a polyethylene oxide. The polyethylene oxide ether oxide/propylene oxide condensation product (leveling glycols having a molecular weight of at least about 1,000 salt), and 1% sodium salt of unsaturated long chain are particularly suitable. Alternatively, the polyethylalcohol sulfate (all percents based on weight of polyene oxide may have, as end caps, either one or two amide yarn, i.e., OWY). A beige shade is achieved, radicals of oxyhydrocarbon such as methoxy, ethoxyl using dye mixture Q of Table III. For each of samples phenoxy, dodecyl phenoxy, nonyl phenoxy and the like. AD, total dye concentration is 0.124% OWY. The The capped polyethylene oxides, especially when capped carpet samples are immersed in baths containing the by aromatic radicals, should have a molecular weight dyes and other dye adjuv'ants at room temperature. Bath of at least 600. The molecular weight and concentratemperature is raised to the boil at the rate of approxition requirement are imposed by the necessity that mately 2 F./min. and held at the boil for one hour enough of the oxide be added to provide a two-phase at which time the pH is 78, as against an initial pH conductive system, i.e., to render the fiber antistatic. of 10-1 1. In each instance, cupric sulfate (5% OWY) Polyethylene oxide compounds which have ends reactive is added and the bath is maintained at the boil for an with the polyamide are excluded since they do not additional /2 hour (final pH of 5.7-6.2). Each dyed form such a two-phase system. Sample is rinsed thoroughly in cold water.

These PEG-modified polyamides may also contain con- The carpet switches are then dried, partially covered vention'al polyamide additives such as delusterants, pigand exposed to the light of a xenon arc in air, in an ment-s, antioxidants, heat stabilizers, plasticizers, adju- Atlas Xenon Weather-Ometer (AXWO). After the invants to increase dyeability, etc. Typical additives are dicated exposure time, shade change is estimated visudisclosed in U.S. Patents Nos. 2,205,722, 2,510,777, ally, based on a scale of 1 to 5, wherein 5 indicates no 2,887,462 and 2,345,533. change, 4 a slight, 3 a moderate and 2 a considerable In addition to polyamide substrates, many other fibershade change. These estimates are reported in Table I forming polymers, if melt blended with a suitable polywhich gives a comparison of carpets containing nylon ethylene oxide, are improved with respect to dye lightwith and without the polyether glycol which were dyed fas-tness and acid dye thermal stability when they have with and without the cupric ion treatment. been impregnated with the cupric ion. It should be noted that many such fibers are so extremely hydro- Table I phobic, e.g., polypropylene, polyethylene terephthalate, and the like, that it is necessary to use a dye carrier or special swelling agent in order to difiuse the cupric ion Shade change into the fiber.

As previously indicated, the important factor is to in- Exposure tune hours 80 160 sure diifusion of the required amount of cupric ion into the fiber. This can be accomplished with a water-soluble PEO m dified nylon, with o 3 cupric salt, e.g., cupric chloride, sulfate, nitrate, acetate, BPE0-m 0dified11y10n. 110 011++ or complex tartrates, oxalates and the like. I%E%%l%2% ig igi fjv it difllijjjj: i: g

The process and fibers of the present invention are especially suit-able for end uses where repeated aqueous scouring is not required. Such end uses include rugs, upholstery, pile fabrics, dress goods, suitings and the The ulated comparisons show that a cupric 1on like. The difiused cupric salt is usually retained to a trealment lncreases the y llghtfaslness (D 0f the satisfactory degree even under mild washing, e.g., during nylon the level of unmOdlfied y a rug shampoo. The normal durability can be supple EXAMPLE II mented by adding a cupric ion salt to the scouring compound provided alkaline PH is avoided Following the procedures of lExampleI, several A samples are dyed, using different acid dye mlxtures to produce EXAMPLE I different shades. DLF results and cupric salt contents in Five percent of a polyethylene oxide ether glycol of parts per million (p.p.m.) are reported in Table II. Dye 20,000 molecular weight is melt blended with polyhexacompositions are specified in Table III.

Table II Dyes used P Q l R S T Shade Gray Beige Brown Green Turquoise. Percent cupric sulfate in bath CuSO,4 5%. OuSO4, 5% CuSO4, 5% OuSO4, 5%.-. CuSO4, 5%. r erin am( .m. 287 379.

SlLade change after AXWO 3- 3+ 3 4-3 4-3.

Sha e change in control yarn 1 1 1+ 1 1+.

EXAMPLE III Using the dye mixtures of Table III and the procedures of Example 1, several samples of carpet A (PEO-rnodified nylon) are dyed in baths containing a lesser concentration of cupric sulfate and in baths containing different concentrations of cupric chloride. Comparative results are reported in the following table.

Table IV Dye mix P Q R S T CuSO.;, 1% OWY:

CuSO in yarn (p.p.m.) 215 222 Shade change after 160 AXWO hrs. 3+ 4 3 3 01101 1% OWY:

OuCl; in yarn (ppm) 305 326 Shade change after 160 AXWO hrs. 4-3 4 4 4-3 4-3 01101:, 5% OWY:

CuCl; in yarn (p.p.m.) 684 638 Shade change after 160AXWO hrs. 3+ 4- 4 4 4-3 When CuCl is replaced by a like amount of cupric acetate, a lesser improvement is noted.

EXAMPLE IV On trying various dye bath procedures, it is noted that the dye bath pH at the time of cupric salt addition is important. At a pH of 9 or above, it is observed that Cu(OH) precipitates. If the bath pH is below about 8.5 (preferably below 8.0) when the salt is added, no precipitation occurs. The drop in the bath pH is, of course, due to loss of the transient base NH OH and is dependent on the time and severity of the boiling process.

When the CuSO of Example II is replaced by an equivalent amount of a copper complex produced by reaction between 1 mole of CuSO and 2 moles of oxalic acid, improved stability is obtained in the pH range of 8.0 to 8.5. The copper concentration in the thus treated PEG-modified carpets is about 200 p.p.m. When tested for DLF, using dye mixtures Q, S and T (Table III), the shade change is one unit less severe than without this copper complex.

EXAMPLE V This example shows the improved thermal stability of dyes on PEG-modified nylon when impregnated with suitable amounts of the cupric ion.

Samples corresponding to A of Example I are prepared and dyed according to the procedure therein described. Dye mixtures Q, S and T of Table III are used. The dye bath contains CuCl (5% OWY). After dyeing, the fibers contain 600-700 ppm. of the copper salt.

The dyed carpet samples are heated for 30 min. in a circulating air oven. The shade changes produced are estimated and listed in Table V, along with similar estimates for a control carpet dyed without use of the copper ion.

6 EXAMPLE VI The essential feature of the invention in improving dye lightfastness of nylon containing PEO is to impregnate the fibers with at least p.p.m. cupric ion. This can be effectively accomplished by boiling the dyed fibers in a water bath containing the cupric salt and at least about 1% of the sodium salt of an unsaturated long chain alcohol sulfate. This procedure avoids the risk of copper precipitation in alkaline dye baths and minimizes jute staining which may occur in an acidic dye bath.

Carpets prepared from nylon fibers containing 5% by weight of PEO are prepared as in Example I, mock-dyed by subjecting them to the dye procedure without adding dye to the bath, then treated as shown in Table VI and rinsed. In each instance, CuSO.; (5% OWY) was added to the room temperature water bath which was then heated to the boil in forty minutes. After rinsing and drying, the fibers were analyzed for copper content.

1 Removed at boil.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A process comprising the steps of: immersing a textile article comprised of PEG-modified nylon fibers in a dye bath containing an acid dyestuff; boiling said bath to dye the article; and boiling the dyed article in an aqueous bath containing at least about 1% OWY of the sodium salt of an unsaturated long chain alcohol sulfate and at least about 1% OWY of a water-soluble cupric salt, said aqueous bath having a pH of less than about 8.5.

2. The process of claim 1 wherein said cupric salt is present in the range of from 15% OWY and is selected from the group consisting of cupric chloride, cupric sulfate and the complex produced by reaction between cupric sulfate and oxalic acid.

3. A process comprising the steps of immersing a textile article comprised of PEG-modified nylon fibers in a dye bath containing an acid dyestuff; boiling said bath to dye the article; transferring the dyed article to an aqueous bath containing at least about 1% OWY of the sodium salt of an unsaturated long chain alcohol sulfate and at least about 1% OWY of a water-soluble cupric salt, said aqueous bath having a pH of less than about 8.5.

4. The process of claim 3 wherein said cupric salt is present in the range of from 15% OWY and is selected from the group consisting of cupric chloride, cupric sulfate and the complex produced by reaction between cupric sulfate and oxalic acid.

5. A process comprising the steps of: immersing a textile article comprised of PEG-modified nylon fibers in a dye bath containing both an acid dyestuff and at least about 1% OWY of the sodium salt of an unsaturated long chain alcohol sulfate; boiling said dye bath until the pH is less than about 8.5; adding at least about 1% OWY of a water-soluble cupric salt to said dye bath; and maintaining said bath at the boil to impregnate the fibers with cupric ions.

6. The process of claim 5 wherein from 1-5 OWY of said cupric salt is added and wherein the salt is selected from the group consisting of cupric chloride, cupric sulfate and the complex produced by reaction between cupric sulfate and oxalic acid.

(References on following page) References Cited by the Examiner UNITED STATES PATENTS Graves.

Graves.

Gray 26045.7 Billings et a1. 260-151 Ruckstuhl et a1. 874 X Csendes et a1. 260145 Van Oot.

Messer 874 Hallden et a1. 281

3,051,696 8/1962 Dettwyler 260-147 3,057,845 10/1962 Liec'hti et a1 260147 X FOREIGN PATENTS 839,456 6/ 1960 Great Britain. 861,354 2/1961 Great Britain. 862,577 3/ 1961 Great Britain.

OTHER REFERENCES Colour Index, 2nd ed., 1956, vol. :1, pp. 1081, 1169 10 and 1318.

NORMAN G. TORCHIN, Primary Examiner. 

1. A PROCESS COMPRISING THE STEPS OF: IMMERSING A TEXTILE ARTICLE COMPRISED OF PEO-MODIFIED NYLON FIBERS IN A DYE BATH CONTAINING AN ACID DYESTUFF; BOILING SAID BATH TO DYE THE ARTICLE; AND BOILING THE DYED ARTICLE IN AN AQUEOUS BATH CONTAINING AT LEAST ABOUT 1% OWY OF THE SODIUM SALT OF AN UNSATURATED LONG CHAIN ALCOHOL SULFATE AND AT LEAST ABOUT 1% OWY OF A WATER-SOLUBLE CUPRIC SALT, SAID AQUEOUS BATH HAVING A PH OF LESS THAN ABOUT 8.5. 